1. Field of the Invention
The present invention relates to an apparatus for evaluating a degree of hardness of an artery of a living subject.
2. Related Art Statement
The technique of stopping a flow of blood through a portion of a patient for making a diagnosis has been used in only measuring a blood pressure of the patient using an inflatable cuff. When a blood pressure is measured using an inflatable cuff, first, the cuff is wound around a prescribed portion (e.g., an upper arm) of a patient and, after the flow of blood through that portion is stopped by the cuff inflated, the pressing pressure of the cuff is slowly decreased, so that the flow of blood is gradually increased, an oscillatory pressure wave occurring to the cuff is detected and, based on the thus detected pressure wave, the blood pressure is measured. Thus, the cuff-using blood-pressure measuring method does not utilize any physical signals that can be detected on a downstream side of the portion the flow of blood through which is stopped by the cuff.
If the change of amount of blood is observed on the downstream side of the portion around which the cuff is wound, it is possible to find that the amount of blood decreases because of the stopping of flow of blood on the upstream side. The Inventor has found that the tendency of decreasing of the amount of blood is influenced by the degree of hardness of artery of the patient.
It is therefore an object of the present invention to provide an apparatus which evaluates a degree of hardness of an artery of a living subject based on a tendency of decreasing of amount of blood because of stopping of flow of blood.
The above object has been achieved by the present invention. According to the present invention, there is provided an apparatus for evaluating a degree of hardness of an artery of a living subject, comprising a blood-flow stopping device which stops a flow of blood through a first portion of the subject; and a blood-amount detecting device which is adapted to be worn on a second portion of the subject that is located on a downstream side of the first portion and which produces a blood-amount signal representing an amount of blood present in the second portion.
According to this invention, when the flow of blood in the portion of the subject is stopped by the blood-flow stopping device, the magnitude of the blood-amount signal produced by the blood-amount detecting device worn on the downstream side of the portion decreases. Since the mode of decreasing of the magnitude of the blood-amount signal changes with the degree of hardness of artery of the subject, the arterial hardness can be evaluated based on the blood-amount signal.
Preferably, the evaluating apparatus further comprises an arterial-hardness determining means for determining the degree of hardness of artery of the subject based on a monotonously decreasing curve of the blood-amount signal produced by the blood-amount detecting device in a state in which the flow of blood through the first portion of the subject is stopped by the blood-flow stopping device.
According to this feature, the arterial-hardness determining means quantitatively determines the degree of hardness of artery of the subject based on the blood-amount signal produced by the blood-amount detecting device.